1 Subversion Kate Hedstrom April 2007

2 Version Control Software System for managing source files –For groups of people working on the same code –When you need to get back last week’s version In the old days, there was SCCS and RCS for file-wise management Then came CVS –Works with whole directory trees –Has a network option for remote access Newest is SVN, which attempts to fix the shortcomings in CVS

3 Getting Started With SVN Tell it where the archive is with a URL: Mine is in nanook’s /archive, visible to Sun and iceflyer For a new archive: file:///local/path or % svnadmin create /local/path

4 Main svn commands import - bring sources into the repository checkout - get sources out of the repository commit - check in changes update - get changes from repository status - find out which files would change on commit diff - find out what changed help

5 Example The svn people advise setting up a directory tree with subdirectories –trunk –tags –branches Your actual code goes in trunk

6 % ls /tmp/cpp branches tags trunk # import whole directory % svn import /tmp/cpp \ file:///local/path -m “initial import” % rm -rf /tmp/cpp # want to be working in checked-out copy % svn checkout \ file:///local/path/cpp/trunk cpp % cd cpp [make some changes] % svn commit

7 # on iceflyer % svn checkout roms % cd roms [make some changes] % svn commit # on cygnus % svn checkout … % cd roms % svn update % make Coordination Coordinate code on multiple systems Coordinate between multiple programmers Can be common version or different branches

8 Updates An update when two people have changed things can involve: –No conflict because changes are in different places –Conflict because two different changes to the same region in the code If there is a conflict this must be resolved by human intervention One option is to revert (undo)

9 Other svn commands add - add a new file or directory to svn control delete - no longer need a file move - rename a file or move to new location merge - merge changes from another branch info - find URL used copy - make branches and tags switch - switch working directory to a different branch

10 Revision Numbers svn uses a database to store the files The whole project as one revision number across the whole project to describe that snapshot Can see the numbers with “svn log” This is different from CVS, which keeps a different number for each file (uses filewise RCS for repository) Every commit creates a new revision number

11 Branch can be just for one or a few files or the whole ROMS tree Branches

12 Tags Tags are handled like branches Create a working version that goes together and make a branch in the tags directory with the name of the tag (release_1.0, say)

13 ROMS Example ROMS comes from a read-only repository: svn checkout hernan_roms Make own repository where that version is the trunk –Copy it to another location without the.svn files –Import it into your repository

14 Now make a branch for your version: svn copy These have to be in the same repository It is currently a copy of the main ROMS code - edit it with your changes and check it back in svn checkout Edit… svn commit

15 So, Hernan has made some changes, what now? Go to your copy of his code from his repository: svn update Make note of files that were added and deleted Copy to the trunk part of your repository: tar cvf - --exclude.svn | (cd../roms_trunk; tar xvf -)

16 In your trunk directory, add and delete the files you noted before: svn add new files… svn delete old files… Check status, then check in: svn status svn commit Make note of the version number

17 Doing the actual merge - in the directory for your branch (URL2): svn merge -r 41:45 Resolve conflicts, if any Check in the update, making note of the revision numbers and svn ci -m “merge from -r 41:45 ”

18 ROMS Summary Each directory has.svn files pointing to its URL

19 Conflicts If there is a conflict, svn will provide you with four files: –The original file (filename.mine) –The older file from the trunk (filename.r41) –The newer file from the trunk (filename.r45) –A merge attempt (filename) The merge failures will look something like:

20 Clean code before <<<<<<<.mine My code ======= New code >>>>>>>.r45 Clean code after Once you’ve cleaned up the mess, tell svn you’re ready: svn resolved filename This will cause svn to delete the extra files and allow a commit to take place You can instead toss your changes with: svn revert filename

21 Learn more Version Control with Subversion, by Collins-Sussman et al., 2004, O’Reilly Online at svn help